noun, noun or participle which takes 'suru'
cutting a nail too short; cutting to the quick
Refers to trimming a fingernail or toenail so short that it exposes the sensitive skin underneath, often causing pain. Can be used as a noun or with する.
深爪をすると痛いですよ。
It hurts if you cut your nails too short.
彼はいつも深爪してしまう。
He always ends up cutting his nails too close.
noun
deep-set nail; nail with a deep quick
Describes a nail where the quick (the sensitive part) extends far forward, making it easy to cut too short. This is a noun-only sense.
深爪の人はネイルケアに気をつけたほうがいい。
People with deep-set nails should be careful with nail care.